Fabrication of efficient natural dye-sensitized Solar Cells using Mediterranean olive leaves as natural dye sensitizer

Abstract

The synthesis of synthetic dyes employed in dye-sensitized solar cells (DSSCs) is often associated with substantial costs and environmental concerns. As a result, there is growing interest in utilizing natural dyes as sensitizers for DSSCs. This paper presents a comprehensive investigation into the extraction of natural dyes from Mediterranean olive leaves using a methanol-based solution, with a particular focus on the impact of different drying times during the dye extraction process on the efficiency of fabricated solar cells. The extracted olive leaf dyes were systematically characterized, encompassing their optical properties analyzed through ultraviolet–visible (UV–Vis) and Fourier Transform Infrared (FTIR) spectroscopy, electrochemical behavior, photovoltaic performance, crystallographic and morphological structures, as well as elemental composition. The research findings unveiled distinctive attributes of the olive leaf dyes, attributable to variations in their charge transfer processes to the band edge of the TiO2 semiconductor. These outcomes were substantiated through comprehensive analyses involving UV–Vis, FTIR, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Notably, the olive leaf dye subjected to a longer drying time (referred to as OLDS1) exhibited an energy level of the lowest unoccupied molecular orbital (LUMO) closer to that of the conduction band of TiO2, facilitating efficient electron transfer. Furthermore, X-ray photoelectron spectroscopy revealed alterations in elemental composition upon dye adsorption onto the TiO2 surface, with a notable reduction in the intensities of the Ti 2p and O 1 s peaks. The OLDS1 dye demonstrated lower charge transfer resistance and recombination rates compared to the shorter drying time for both fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO)-based natural DSSCs (NDSSCs). Importantly, the choice of substrate material, specifically FTO and ITO, significantly influenced the NDSSC performance. The FTO/TiO2/OLDS1 configuration exhibited remarkable characteristics, including a high fill factor (FF) of approximately 0.73 and an efficiency of 0.31 %, accompanied by a short-circuit current density of 0.662 mA/cm2 and an open-circuit voltage of 0.642 V. These results highlight the crucial role of drying time and substrate selection in the fabrication of NDSSCs utilizing Mediterranean olive leaf extracts, with the FTO/TiO2/OLDS1 configuration emerging as the most promising and efficient combination.